This invention relates to security systems in which access is selectively permitted on the basis of data encoded onto a card which a user inserts into receptacles at remote locations in the system. More specifically, the invention pertains to a system for limiting access to the programming functions for such a security system, so that only those personnel who insert specially encoded cards are entitled to change the control index listing of the system. This listing is used to provide data as to those personnel who are entitled to access at specific remote locations at specific times.
Prior art static magnetic card readers for controlling access through electrically operable devices, such as doors, turnstiles, printers, etc., have been utilized for some time. Such systems typically include cards on which data is encoded, the data being used for controlling access. The card or badge is typically inserted into the slot of a reader which reads and decodes the encoded data on the card. Advantageously, the data is encoded as a plurality of magnetically polarized spots in a strip of magnetic material. Such encoded data normally includes an identification number or numbers identifying the card holder. During use, this number encoded by the card is compared with a number or numbers stored either in the remote terminal or in a central computer terminal to ascertain whether the individual inserting the card is entitled to access to a building, room, parking lot, or the like, at the particular time of day at which the card is inserted.
In one prior art embodiment, the magnetically polarized spots are used to directly actuate a reed relay or other moving switch mechanism located within the reader. The state of the art system is exemplified by U.S. Pat. No. 3,686,479 entitled Static Reader System for Magnetic Cards, assigned to A-T-O Inc., assignee of the present invention, employing electromagnetic solid state sensors disclosed and claimed in U.S. Pat. No. 3,717,749, also assigned to A-T-O Inc. The use of such devices in an on-line system employing a central processor and plural remote units is described in U.S. Pat. No. 4,004,134, also assigned to A-T-O Inc. Such systems have been found to be very reliable and are in use as access control systems in a number of different industries, universities, and in government installations.
It has been common in the prior art to include control storage in such systems which store a list of personnel ID numbers, along with data defining which remote terminals shall be open to which particular employees at specific times of day. In systems which have not included a central processor (where each remote location includes a stand-alone terminal), this storage for identifying employees and times of day for access through that particular terminal is located in the remote terminal itself. In those prior art systems embodying a central processor, it has been common to utilize the remote unit to transmit identification data read from the identification card to the central processor. At the central processor, this identification data is utilized as an address to locate data in a table which defines those remote terminals and times of day at which this particular individual is allowed access. This latter system is described in some detail in U.S. Pat. No. 4,004,134, which is hereby incorporated by reference.
Such prior art systems have typically permitted the owner or operator of the secured facility to change the look-up table and thereby alter which employees have access through which remote locations at particular times of day. The security of the entire system of such prior art devices, however, is degraded by utilizing devices such as keylocks to limit access to the program control for changing the data in the control storage. Thus, it is typical in prior art installations to include a keyboard within the central processor (or a remote terminal in a stand-alone system), which keyboard is protected by lock and key from unauthorized access. In order to alter the control storage, one has only to physically break into the system, and one could then freely program the storage to permit access to unauthorized persons at particular times of day and particular remote units as one might choose. Since the security of the system is only as effective as the security of this control storage, such prior art systems are susceptible to clandestine entry by persons familiar enough with the system to be able to program it and capable of physically breaking into the locked enclosure.